Hearing aids comprising ear pieces which are to be secured in the auditory canal of the user, may comprise an expandable part which is expanded in order to secure the ear piece in the auditory canal of the user. Such an expandable part is used instead of common ear domes made of stiff silicone or polyurethane and provides increased comfort and fitting rate for hearing aid users. In order to position such an expandable ear piece, it is brought in a compressed state to allow insertion into the ear canal. U.S. Pat. No. 7,362,875 discloses an expandable ear piece having a frame to facilitate compressing and expanding of the ear piece. Prior to insertion into the ear canal, the ear piece is compressed by the user. Once inserted, the frame expands and conforms to the ear canal. A drawback is that a specifically constructed frame is required.
U.S. Pat. No. 7,425,196 discloses an expandable ear piece having a balloon capable of being inflated and deflated. Prior to insertion into the ear canal, the balloon is brought in a deflated state. Once inserted, the balloon is inflated by pumping air into the balloon, which thus expands and conforms to the ear canal. However, in the deflated state the balloon is highly flexible and pliable and hence is difficult to be inserted in the ear canal.
From an auditory usability point of view, it is desirable that the walls of the inflatable part are as thin as possible, as this reduces the occlusion effect. Furthermore, a very thin wall material provides a better seal as compared to a thicker foil as it conform to the ear canal more easily.
However the thinner the wall is, its unfolding will be nosier from a completely collapsed state. Moreover, as the ear piece is unfolded inside the auditory canal (i.e., close to the ear drum), even low levels of noise will be perceived as uncomfortable by the user.
It is an object of one or more embodiments of the present invention, to provide an ear piece for a hearing aid which alleviates the above drawbacks